Fang initially treats Tiara indifferently, but acknowledges her as a valuable ally and someone he cares about. The two often bickered a lot initially, with Fang calling her names (much to her masochistic pleasure) and berating her gaudy lifestyle and habits.
It wasn't until the hot springs event where upon being ambushed by an enemy that tried to kidnap Eryn and Tiara that Fang risked his life to save Tiara, despite falling off a cliff into a river and not having Eryn to back him up. Tiara and Fang shared a private moment wherein she told him to "Not fall in love with her" to Fang's confusion.
This cryptic statement turned out to have relevance later though, when Tiara is killed later during the summoning of the Goddess. It is at this point that Fang wishes to go back to a time that Tiara was alive, and as such Fang and Eryn get transported back to the past, right before he met Tiara.
Initially distrusting, even more so than when they first initially met calling him a "stalker" and being creeped out by his ability to predict future events. Fang reassured her in the same way he did when he first met her, protecting her from a bandit that accosts her (yet again) and earning her trust, for the moment.
At the end, if you have done everything the game ask, you will be rewarded with The Tiara Ending.
Self-Proclaimed apprentice of Fang, Galdo and Fang share a bond that can only be considered as mentor/student. Galdo initially was working for Zenke and the Dorfa Company, but upon being defeated by Fang, he apologized to Zenke for losing, and was about to be cut down by Zenke before Fang stepped in and saved Galdo's life. Amazed by his selflessness for a person who was just his enemy, Galdo extends his gratitude by joining the party.
It is Fang that defends Galdo from Tiara's initial outbursts of distrust, claiming that Galdo was a good person. Galdo is constantly trying to show off his talent to Fang, who acknowledges that Galdo is an asset to the party.
Galdo and Fang have a similar mindset, as they tend to say the same lines at the same exact time, or share similar viewpoints about certain people, such as Sherman.
Fang and Harley have almost a sibling-like relationship, almost. Harley likes to playfully tease Fang in some of the sub events they have together, usually making Fang embarrassed/uncomfortable only for her to begin going off on Fairy lectures. Like everyone else, Fang sees Harley as a good ally, and is especially fond of her fairy, Bahus for cooking excellent food for him all the time.
Eryn and Fang are both Fairy and Fencer respectively, and as such are subject to a "special bond" that exists only between fairy and fencer, according to Harley. Initially wanting nothing to do with being a Fencer, Fang tries his hardest to get out of being a Fencer until Eryn mentions that her memories are missing and that if left alone she would surely wither and disappear. Fang's conscience gets the better of him and he agrees to help Eryn solely for the sake of getting her memories back under one condition: That he would control his fate, and nobody else.
Despite everything Fang and Eryn say, Eryn and Fang make almost a perfect match as Fairy and Fencer. Both of them have been shown to not be early-risers and a bit of a slob from time to time, as well as both of them being particularly enthusiastic about showing off their skills. It eventually gets to the point where Eryn can sense Fang's desires to the point where communication becomes unnecessary for them to understand each other.
Like Tiara, after the hot springs incident, she grows to respect Fang a bit more as a fencer and sees him as someone reliable.
After Tiara dies and Fang and Eryn return to the past, She confessed that she was in love with Fang when he playfully asked if she was falling in love with him. Possibly due to their increased bond, Eryn's Fury undergoes a transformation after breaking down, resulting in Fang and Eryn being stronger than ever before.
Sherman is considered to be the complete opposite as Fang by almost everyone in the group. Being kind, polite, well mannered and having a strong sense of justice he is always seen as a more reliable and better version of Fang much to his dismay.
Due to this Fang has a sense of jealously towards Sherman and distaste for him. However later on Fang is shown to rival and even surpass Sherman causing him to at least acknowledge Fang as a valuable fighter.
Although Fang generally shows annoyance towards Sherman he still values him as a friend and powerful ally.